Dopamine receptors in human lymphocytes: Radioligand binding and quantitative RT-PCR assays

Abstract

Analysis of dopamine receptors (DR) in lymphocytes of the human peripheral blood mononuclear cell (PBMC) fraction is an attractive tool for evaluation of functional properties of dopaminergic function underlying variation in complex psychological/psychopathological traits. Receptor binding assays (RBA) with selective radioligands, which are widely used in CNS studies, have not produced consistent results when applied to isolated PBMC. We tested the assay conditions that could be essential for detection of DR in human PBMC and their membrane preparations. Using [3H]SCH23390, a dopamine D1-like receptor antagonist, we demonstrated the presence of two binding sites in PBMC-derived membrane fraction. One of them is characterized by the Kd value consistent with that reported for D5 dopamine receptors in human lymphocytes, whereas the other Kd value possibly corresponds to serotonin receptor(s). Although D5 receptor binding sites in PBMC membranes could be characterized by binding assays, the low protein expression and the large volume of blood needed for membrane preparation render the binding method impracticable for individual phenotyping. In contrast, real-time RT-PCR may be used for this purpose, contingent on the relationship between DR expression in the brain and in lymphocytes. The expression of the DRD2-DRD5 genes, as detected by this method, varied widely among samples, whereas the DRD1 expression was not detected. The expression levels were comparable with those in the brain for DRD3 and DRD4, and were significantly lower for DRD2 and DRD5.

Dopamine Receptor Gene Expression Changes in Peripheral Blood Mononuclear Cells from Schizophrenic Patients Treated with Haloperidol and Olanzapine

“…This suggests that PMC molecular markers may be useful in investigation of the mechanism of action of treatment over time. The PMC gene expression changes occurred in parallel to clinical improvements in schizophrenic patients consistent with the study of Kirilova et al (16). Also, the profile of dopamine receptor genes may be specific with type oftreatments that report similar results in other studies (17)(18).…”

Human Immunodeficiency Virus (HIV) Infection of Human Macrophages Is Increased by Dopamine

“…DRs are differentially expressed on dopaminergic neurons throughout the brain and can also be found on a number of other cell types, including immune cells and glia. 25,37,38,57 DA plays an important role in many neurological disorders such as Parkinson's disease but has not been well examined in the context of HIV-induced neuropathology. In simian immunodeficiency virus-infected macaques, a model for neuroAIDS, administration of the DA-enhancing substances L-DOPA and selegiline increased CNS viral load and accelerated the development of neuropathology.…”

“…25 Classically, DRs have been studied on neurons, but DR expression has also been reported in several types of peripheral blood leukocytes, including T lymphocytes and monocytes. [37][38][39] Dopamine receptors have been shown to modulate the immune function of T lymphocytes. 25,40,41 A recent study showed D1R on human macrophages, 24 but the expression of other DRs and the functions of DRs in this cell type have not been well characterized.…”

Dopamine Inhibits the Effector Functions of Activated NK Cells via the Upregulation of the D5 Receptor

“…Indeed, both primary and secondary lymphoid organs contain high levels of dopaminergic nerve terminals (3)(4)(5). Moreover, many circulating immune cells, including monocytes, neutrophils, eosinophils, B cells, T cells, NK cells, and dendritic cells (DCs), constitutively expresses DA receptors (DARs) on their surface (6)(7)(8)(9)(10). The engagement of DARs on these immune cell compartments is associated with the regulation of several important cell functions, such as cellular proliferation and division, cytokine production, cell polarization, and migration (11)(12)(13)(14)(15)(16)(17).…”